David Cameron has promised a Government commitment to ban wild animals such as lions, tigers and elephants in circuses will be made law - despite the fact that it was left out of the Queen's Speech.

In a letter to the charity Animal Defenders International (ADI), the Prime Minister has written: "Let me reassure you that it remains our position that the use of wild animal acts in travelling circuses is an outdated practice and that we will introduce a ban as soon as Parliamentary time allows."

Campaigners thought the policy had been dropped because there is so little time now to bring the legislation forward before the next election.

The ban has been supported by a long list of celebrity campaigners including Eddie Izzard, Ricky Gervais, Julian Clary, Moby, the actors Dominic West and Judi Dench, as well as Stanley Johnson, the former MEP and conservationist.

Image:Animal Defenders International has previously captured footage of cruelty

Mr Johnson told Sky News that it was intolerable to use the animals in circus acts and he was deeply disappointed that the policy was not included in June's list of bills announced by the Queen.

He is publishing the second volume of his memoirs next month and includes a picture of himself meeting the Prime Minister, alongside Peter Tatchell in April this year.

Its caption reads: "Prime Minister David Cameron promises us that the government will ban the use of wild animals in circuses. We are still waiting!"

Fleur Dawes from the charity said that even if that was not happening the circus life was in itself enough to cause suffering for animals.

There are only two circuses left in Britain that still have wild animals, including tigers, lions, zebras, snakes, reindeer, raccoons, foxes, camels and an Ankole.

One - called Peter Jolly's Circus - is operating in Buckley, near Chester, and has attracted protesters.

Both refused to give a statement to Sky News but have argued that they care for the welfare of the animals and are subject to regular checks by the Government - brought in after abuse was highlighted in other circuses that have since closed.

Image:Ricky Gervais is one of the famous faces supporting a ban

A spokeswoman for the Department for Environment, Food and Rural Affairs said: "We are committed to banning the use of wild animals in circuses and will introduce legislation as soon as parliamentary time allows.

"As we work towards a ban we have a strict system in place to ensure the welfare of all 23 circus animals in England.

"This includes announced and unannounced inspections, care plans for every animal, regular veterinary inspections and a retirement plan for each animal."